Devitrification -- Help Please!

[LadyGlass108]

Having a problem with devit and I don't understand what is causing it, and if it can be fixed once present on clear glass. It seems to happen the most when I'm stretching a neckpiece longer and it appears to be on the outside of the piece with frit on the interior. I would very much appreciate some help on this, and I've searched all over the forum but the info must be burried.

[Eileen]

I'm confused with what you are doing?
Soft glass or boro? Tubing or encased frit?

Can you put a photo up, that would be much easier to see what the problem might be.

[designsbykurato]

It sounds like you are encasing a frit bead and that the frit is bleeding out from the sides, try to make certain the edges are completely covered in clear.

[LadyGlass108]

I appreciate the replies. My daughter is going to work a piece shortly and I'll post a picture later for possible feedback. I'm not even sure if I'm using the correct terminology -- I think it's devit or stress/stretch marks.

Boro, functional spoon, frit inside heavy wall tube, Red Rocket, oxycon/propane.

She does the pipes, I make boro beads & pendants, and since I work smaller stuff I don't experience this problem like she does.

[Talonst]

This can happen in boro when the glass isn't heated evenly all the way through. The section being pulled needs to be hotter most likely. Before pulling out take the piece out of the flame and pause while rotating to allow time for the surface heat to sink into the thickness of the tube and distribute itself more evenly - then pull slow at first then faster - like pulling a point.

Surface devit and stretch marks can also show up when the glass is still being pulled and the surface has begun to stiffen. In this case pulling faster or heating and pulling smaller sections at a time might work.

Flame is also an issue - a bushier radiant heat type of flame delivers a more enveloping heat. Too focused causes hot spots and uneven heating

People often have these types of problems in tubing when they first start because they're still developing their rotation skills. When the glass starts to get loose they get nervous when they see it start going off center and pull too soon before the glass is molten enough.

It's also helpful to gather the tube before stretching - this is pushing slightly while heating the tubing section so there is extra glass to pull out.

[Talonst]

Also see this http://jamesfbyrnesblownglass.com/ne...-demonstration

Should answer most of the questions on constrictions and tapers

[LadyGlass108]

Wow... thanks so much for the info. As it turns out today, she really cranked up the heat on the torch (which is new) and had a very successful day with 4 or 5 nice pieces in the kiln now. No sign of stretch/devit. She's definitely not a beginner, but I think the switch from a Major/Minor to the Red Rocket threw a wrench in the works as a learning curve.

Next I'll have to ask some questions on my own behalf... I am a beginner (one year on a Mini CC, oxycon/propane, boro beads & pendants) and we live at about 6500' above sea-level. I'm having difficulty getting nice striking colors and most seem to turn kinda milky tan or greenish. More propane or more oxy? And, how does one strike color that is encased in a pendant?

Thank you all so much for your wisdom and patience with a noobie!

[Eileen]

Check out this thread in the boro room, and look at what kiln striking does to some colors.
I'm just reading up on boro, don't have any real practical experience yet, but it made an impression on me!

http://lampworketc.com/forums/showthread.php?t=243016

[LadyGlass108]

Thanks Eileen. I don't have time yet to check out the thread -- hopefully tomorrow!!

Here is a picture of the devit or stretch/stress marks my daughter had been getting. We think we have it figured out since she really cranked up the heat on her new torch. Can this piece be put back in kiln and reheated to a working temp to try to retorch and work the haze out?